1. Field of the Invention
The present invention relates generally to computer-aided design and engineering, and more particularly to a method and apparatus for improved associative drafting of geometric models.
2. Description of the Related Art
During the drafting process for creating geometric models, a user is called upon to input a great deal of information which a modeling system employs to assist the user in creating geometric models for various CAD/CAM applications. Often the draftsperson is required to mentally determine what a cross-section would look like and then manually create the respective section by drawing unassociated curves on the drawing to generate the correct sections for the drafting system.
Moreover, while some drafting systems aid the draftsperson in creating a section by automatically determining the necessary curves, and establishing the section therefrom, if the model is changed, for example, due to editing or design changes, the draftsperson is required to manually repeat most of the original creative input, taking into account the relevant desired changes, for the system to regenerate a new section. Thus updating the model requires manual intervention for current drafting systems. This results in unnecessary lost work every time a model is updated.
A few drafting systems create cross-sections and receive user input concerning the dimensioning of cross section and model change. Once a change occurs in the model, the section view updates automatically without the actual cross-section cut itself changing its location if it needs to. Thus, if a draftsperson initially creates a section cut through specified entities of an object, and then the draftsperson moves or modifies one of the entities in some fashion, these drafting systems will either show the entity as still present as it previously existed, will indicate the entity is gone if it was moved, or will cut through the entity at an undesirable location. In other words, the section will no longer appropriately reflect the changed entity because current drafting systems do not track geometric entities in connection with an associated section line.
After a section is created a user typically manually places a number of reference dimensions on the section view itself. Though the section will be regenerated (redrawn) if the model changes, those reference dimensions all disappear, thereby resulting in additional lost work as a user is then obliged to manually reinput those dimensions.